Architecture involves problem-solving. Typically it means maximising comfortable space for cost in housing or office projects yet when it comes to designing for incarceration and the judicial system, there are other factors at play. Many of the usual rules still apply – prisoners should receive ample natural light, for example – but they are also being punished, so how should a person’s wellbeing be balanced with paying penance? We explore best practice in the design of prisons, police stations and courthouses in search of some arresting architecture.